Plug cap



E. E. FOLSOM PLUG -GAP March 5, 1940.

Filed Jun 10, 1938 Patented Mar. 5, 1940 PLUG CAP Elwood E. Folsom, Trumbull, Conn, assignor to General Electric Company, a corporation of New York Application June 10, 1938, Serial No. 212,991

3Cllims.

This invention relates to plug caps for use with outlet receptacles, and more particularly to a plug cap which is adapted to be secured to aconductor to form a cord set.

It is an object of this invention to provide an improved construction and arrangement in a plug cap of the type described which comprises relatively few parts, whichmay be assembled upon a conductor at low cost and which further pro vides for a secure mechanical and electrical connection between the conductor and the elements of the plug cap.

In the accompanying drawing, Fig. 1 is a view of a plug cap illustrating the invention with part of the plug cap broken away to show the interior construction; Fig. 2 is a sectional view through the plug cap along the line 2--2 of Fig. 1, while Fig. 3 is an exploded view of the elements of the plug cap.

Referring to the drawing, the numeral 9 indicates a plug cap construction which is adapted to be connected to the end of an electrical conductor ll thereby forming a cord set. The plug housing III, which may be molded from a suitable molding compound such as a phenolic condensation product and filler, is formed in two parts designated l2 and I3, each of the parts being identical in size and shape and being adapted to mate with the other to secure the conductor H and the terminals of the plug cap within the body of the housing. Inasmuch as the parts of the housing are identical, only one part will be described it being understood that the remaining part is constructed similarly in every respect.

Referring more particularly to Fig. 3, the part 02 of the housing is provided with a centrally located recess I4 extending axially of the length of the housing part. The recess I4 is divided midway of the length of the housing and extends to the bottom i5 01' the housing in bifurcated form, thereby forming the opposed longitudinal recesses l8 and II on each side of the housing. The recesses I6 and II are formed by'the shoulder l8 upstanding from the base of the housing part and which is provided with a rounded edge III for a purpose to be described later. In order to accommodate the terminals of the plug cap, a longitudinal channel 20 is formed in each of the recesses Ii and II. The channels 2| are provided at their upper ends with transverse recesses or slots 2| which extend inwardly toward each other from the channels 20 toward the shoulder II. In addition, the channels are provided with narrow extended portions 22 which project upwardly above the transverse slots 21.

As shown more particularly in Figs. 2 and 3, the longitudinal channels 20, the slots 2| and the extensions 22 are cut deeper than the recesses ii and II to accommodate the terminal prongs of the plug cap. The shoulder i8 is flush 5 with the face 23 of the housing part l2 so that the recesses l6 and I! may accommodate the conductor Ii.

Each of the terminal prongs comprises a stripof sheet metal 24 which is bent back on itself at 25 to form parallel leg portions 26 and 21. The leg 21 is provided with'an inwardly extending projection or arm 28 which is disposed at an angle 'to the axis of the terminal prong, preferably at a right angle thereto. The remaining leg 26 is provided with an integral extension 29 projecting beyond the arm 28 in a direction parallel to the axis of the terminal prongs. In constructing a terminal prong a strip of sheet metal of appropriate length istaken and the projection or arm 28 formed therein. The strip is then bent back upon itself to form. the parallel leg portions 26 and 21 with the bend being located at the proper point to insure the correct standard length of the completed prong termi- 25 nal. Due to the bend 25 in the metal strip the length of the leg including the extension 29 will vary somewhat because the radius of the bend will vary slightly in individual cases. This slight variation in the length of the leg 26 is taken 30 care of by increasing the length of the slot 22 to accommodate the extended portion of the leg 26.

A terminal prong is assembled upon each of the insulated wires 30 and ii forming the electrical conductor. In assembling the terminal prongs upon the wires of the conductor, the legs. of the prongs are spaced slightly from each other so that the bared ends 32 of the wires may be inserted between the leg portions of the terminal prongs. The leg portions and the bared ends of the conductors are then forced together and spot welded as shown at 33. By spot welding the terminal prongs to the conductor, as shown in Figs.

1 and 3, it is possible to secure a permanent electrical and mechanical 'bond between the terminal prongs and the wires and to form a terminal prong having leg portions which are in substantially parallel alignment, because the copper wires of the conductor can be spread out and flattened down during the welding operation to take up very little room. Moreover, the operation of welding the contact prongs to the conductors can be accomplished at low cost and obviates the necessity of employing separate fastening means such as a terminal screw. The assembled structure is very compact and can be easily assembled within the recessed construction 01. the housing parts.

In assembling the contact structure within the housing parts the terminal prongs 24 are inserted within the channels which are wide enough to accommodate both legs of the terminal prongs. The projections 28 fit snugly within the recesses 2| while the extensions 29 are seated within the extended slots 22. It will be apparent that the projections 28 cooperate with the slots 2| to prevent axial movement of the contact prongs relative to the body of the housing. In other words, it is impossible to pull the terminal prongs out from the housing because of the interengagement of the projections 28 and the slots 2|. In order to maintain the contact prongs in spaced parallel relationship with each other, the extended portions 29 make contact with the sides of the slots 20 and 2|. The fact that the extended portion 29 of the contact terminal closely engages the wall of the slot 22 above the projection 28 makes it impossible to tilt the terminal prong in the slot about the projection as a pivot so that the terminal prongs are out of parallel alignment. At the same time the slot 22 is made long enough to accommodate the slight variation in the length of the leg 26 occasioned by the bend 25, this structure being shown by Fig. 1 at 34.

After assembling the contact structure upon one of the housing portions the remaining portion is placed over the other, and the two portions are secured together by means of a rivet 35 passing through openings 36 provided in each portion. In order to provide a smooth surface on the exterior of the housing, the openings 36 are countersunk, as at 31, to receive the head of the rivet. The depth of the recesses I4, l6 and I1 and the thickness of the insulated conductor are so proportioned that the insulation on the conductor is compressed between the two portions of the housing when in assembled position as shown at 38 in Fig. 2.

In this position, the insulated wires 3|! and 3| forming the conducting cord cooperate with the sides of the recesses l6 and I1 and are compressed between the edge l9 of the shoulder and the sides of the recesses to provide a firm frictional grip between the cap portion and the insulation on the conductors A transverse ridge 39 is provided in each of the recesses I4 and as the conductor is gripped between the two portions 01' the housing the ridge 39 is embedded within the insulation of the conductors to form a strain relief means In the instant case the insulation on the conductors is formed of rubber so that it may be compressed readily between the housing portions and in order that the transverse ridges 39 may secure a firm gripping action on the insulation.

By providing a housing structure which securely grips the insulation on the cord, it is possible to secure a construction which will absorb the strains and pulls incident to rough usage. Moreover, by welding the conducting wires to the terminal prongs, an excellent mechanical and electrical connection is secured between the wires and the contact terminal prongs and one which will withstand the stress and bends incident to use of the cord set. By the construction described, it is possible to manufacture a plug cap for a cord set at small cost; the two parts of the housing are identical in structure and may be 8 formed from a single mold and the contact structure is easily and quickly assembled within the housing and secured in assembled relationship by a single fastening means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a plug cap structure, a contact formed of sheet metal bent back upon itself to form parallel legs, the end of one of said legs being bent substantially at right angles to the axis of the contact to form a projection, the other of said legs having an integral extension parallel to the axis of the contact, a cord having a conductor disposed between the legs of said contact and spot welded thereto, and a two-piece body surrounding said contact assembly and being provided with a plurality of recesses to accommodate said cord and contact structure, said projection cooperating with one of said recesses to prevent displacement of said contact upon said body, said extension cooperating with another of said recesses to maintain said contact and body in axial alignment.

2. In a device of the class described, a twopart housing having a plurality of recesses formed therein, terminal prongs comprising strips of metal bent back upon themselves to form parallel legs, an insulated conductor comprising wires having bared ends one of which is inserted between the legs of each terminal prong and is spot welded thereto, said assembled terminal prongs and wires being disposed in certain of said recesses and said conductor being disposed in another of said recesses, transverse ridges projecting from said housing into said other recess to engage said insulated conductor, and means securing the parts of said housing together whereby the insulation on said conductor is compressed by the parts of said housing and said projections grip said insulation to fasten said housing to said conductor.

3. In an electric plug, a two-part housing, each part having spaced longitudinal recesses formed therein and having slots extending angularly from said recesses toward each other, there being 50 second slots in each of said parts extending parallel to and beyond said recesses, terminal prongs comprising strips of metal bent back upon themselves to form legs, one of the legs of each prong having an arm projecting at an angle thereto and the other leg having an integral extension parallel to the prong, an insulated conductor comprising wires having bared ends one of which is inserted between the legs of each terminal prong, the legs of each prong being welded thereto, said assembled terminal prongs and wires being disposed in said longitudinal recesses with the projecting arms being placed in said angularly extending slots and said integral extensions being disposed in said second parallel slots, and means fastening the parts of said housing together to clamp said terminal prongs and conductor within said housing.

ELwooD E. FOLSOM. 

